U.S. patent application Ser. Nos. 181,974, filed Aug. 28, 1980 and now abandoned, 295,400, filed Aug. 21, 1981, and 572,678, filed Jan. 20, 1984, all of which are now owned by the assignee of the present application and are here incorporated by reference, disclose flexible sheet heaters including a pair of longitudinally-extending (typically copper) conductors, and a semi-conductor pattern comprising a plurality of transversely-extending bars spaced apart from each other and extending generally between and electrically connected to the conductors. The heaters there disclosed provide superior performance and substantially even heat distribution, and are useful in a wide range of applications.
There are circumstances, however, in which constant heat distribution over a regular parallel-sided heated area is not desired. For example, targets used to produce thermal images which will be seen by an infrared sight should produce an irregular heat pattern which approximates the thermal image produced by the man, tank, or other target represented.